Liquid discharge apparatus and method for producing the same

ABSTRACT

A liquid discharge apparatus includes: a pressure chamber; a film covering the pressure chamber; a piezoelectric element disposed on the film and including a piezoelectric part, a first electrode, and a second electrode, wherein the first electrode is disposed on a first side of the piezoelectric part facing the pressure chamber, and the second electrode is disposed on a second side of the piezoelectric part opposite the first side; a gold trace connected to the first electrode or the second electrode; and a first metal part made of a metal material except for gold and positioned between the film and the gold trace. The first metal part is laminated with the gold trace.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2014-264175 filed on Dec. 26, 2014, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a liquid discharge apparatus configuredto discharge liquid and a method for producing the liquid dischargeapparatus.

Description of the Related Art

As a liquid discharge apparatus, Japanese Patent Application Laid-openNo. 2013-111819 discloses an ink-jet head including piezoelectricelements for discharging liquid. The ink-jet head is provided with achannel forming substrate which includes pressure chambers, andpiezoelectric elements provided on the channel forming substrate tocorrespond to the pressure chambers respectively. Each of thepiezoelectric elements includes a piezoelectric film, a lower electrodefilm disposed on the lower side of the piezoelectric film, and an upperelectrode film disposed on the upper side of the piezoelectric film. Thelower electrode film is an individual electrode individually providedfor each piezoelectric element. Upper electrode films of thepiezoelectric elements are electrically connected with each other andfunction as a common electrode for the piezoelectric elements. A Wire(lead electrode) made of gold is connected to the lower electrode filmof each of the piezoelectric elements.

SUMMARY

In each of the piezoelectric elements of the ink-jet head described inJapanese Patent Application Laid-open No. 2013-111819, it is preferredthat the wire have a large thickness to improve the reliability ofelectrical connection of the wire connected to the lower electrode filmand to reduce the electrical resistance of the wire. However, in theink-jet head described in Japanese Patent Application Laid-open No.2013-111819, the wire connected to each lower electrode film is made ofgold which is expensive noble metal. Thus, increasing the thickness ofeach wire requires a larger amount of gold, thereby increasingmanufacturing costs.

An object of the present teaching is to improve reliability ofelectrical connection of each wire and to reduce electrical resistanceof each wire white avoiding manufacturing cost increase.

According to a first aspect of the present teaching, there is provided aliquid discharge apparatus, including: a pressure chamber; a filmcovering the pressure chamber; a piezoelectric element disposed on thefilm and including a piezoelectric part, a first electrode, and a secondelectrode, wherein the first electrode is disposed on a first side ofthe piezoelectric part facing the pressure chamber, and the secondelectrode is disposed on a second side of the piezoelectric partopposite the first side; a gold trace connected to the first electrodeor the second electrode; and a first metal part made of a metal materialexcept for gold and positioned between the film and the gold trace,wherein the first metal part is laminated with the gold trace.

In the present teaching, the gold trace connected to the first electrodeor the second electrode is stacked on the first metal part made of ametal material other than gold. Stacking the gold trace on the firstmetal part increases the substantial thickness of the trace, therebypreventing disconnection of the trace and the like. Further, stackingthe gold trace on the first metal part produces the effect of loweringthe substantial electrical resistance of the trace. The first metal partis made of a metal material other than gold, i.e., can be made ofinexpensive metal material. This improves the reliability of electricalconnection of the trace and lowers the electrical resistance of thetrace while reducing material costs.

The first metal part is made of a metal material except for gold, whichis very stable material. Thus, the stability (for example, corrosionresistance) of the first metal part is lower than that of the goldtrace. To solve this problem, it is preferred that the gold trace madeof stable Au is disposed on the upper side and the first metal part isdisposed on the lower side of the gold trace. In a case that the traceis made of gold, a thin base layer, called an adhesion layer or seedlayer, is typically provided on the lower side of a gold layer toimprove adhesiveness or to form the gold trace through film formation,plating, or the like. Namely, the concept of “gold trace” according tothe present teaching includes not only the gold layer but also the baselayer. Accordingly, the liquid discharge apparatus of the presentteaching includes not only the gold trace but also the first metal part,the gold trace provided with the gold layer and the base layer disposedon the lower side of the gold layer, the first metal part made of ametal material other than gold.

According to a second aspect of the present teaching, there is provideda method for producing a liquid discharge apparatus, including: forminga first electrode on a film formed on a substrate; forming apiezoelectric part on the first electrode; forming a second electrode onthe piezoelectric part; forming a metal part on the film by a metalmaterial except for gold; and forming a gold trace on the metal part toconnect to the first electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a printer according to an embodimentof the present teaching.

FIG. 2 is a top view of a head unit of an ink-jet head.

FIG. 3 is an enlarged view of the portion A in FIG. 2.

FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3.

FIGS. 5A to 5C depict manufacturing steps of the ink-jet head, whereinFIG. 5A depicts a step of forming a vibration film, FIG. 5B depicts astep of forming a lower electrode, and FIG. 5C depicts a step of forminga piezoelectric body.

FIGS. 6A to 6D depict manufacturing steps of the ink-jet head, whereinFIG. 6A depicts a step of forming a conductive film for an upperelectrode, FIG. 6B depicts a step of etching of the upper electrode,FIG. 6C depicts a step of forming a metal part, and FIG. 6D depicts astep of forming a wire.

FIGS. 7A to 7C depict manufacturing steps of the ink-jet head, whereinFIG. 7A depicts a step of etching a channel substrate, FIG. 7B depicts astep of joining a nozzle plate, and FIG. 7C depicts a step of joining areservoir forming member.

FIG. 8 is a cross-sectional view of an ink-jet head according to amodified embodiment.

FIG. 9 is a cross-sectional view of an ink-jet head according to anothermodified embodiment.

FIGS. 10A to 10E each depict a cross-section of the vicinity of apiezoelectric actuator of an ink-jet head according to still anothermodified embodiment.

FIG. 11 is a cross-sectional view taken along the line XI-XI in FIG.10A.

FIG. 12 is a cross-sectional view, of an ink-jet head according to yetanother modified embodiment, which corresponds to FIG. 11.

FIGS. 13A and 13B each depict a cross-section of the vicinity of apiezoelectric actuator of an ink-jet head according to further modifiedembodiment.

FIG. 14 is a cross-sectional view of an ink-jet head according to stillfurther modified embodiment.

DESCRIPTION OF THE EMBODIMENTS

An explanation will be made about an embodiment of the present teaching.The schematic configuration of an ink-jet printer 1 will be explainedfirst with reference to FIG. 1. The front, rear, left, and rightdirections depicted in FIG. 1 are defined as “front”, “rear”, “left”,and, “right” of the ink-jet printer 1, respectively. Further, the frontside with respect to the paper surface of FIG. 1 is defined as “up” andthe back side with respect to the paper surface is defined as “down”. Inthe following, the explanation will be made by appropriately using thefront (side), the rear (side), the left (side), the right (side), the up(side), and the down (side) defined as described above.

<Schematic Configuration of Printer>

As depicted in FIG. 1, the ink-jet printer 1 includes a platen 2, acarriage 3, an ink-jet head 4, a conveyance mechanism 5, a controller 6,and the like.

A recording sheet 100 as a recording medium is placed on the uppersurface of the platen 2. The carriage 3 is configured to reciprocate inan area facing the platen 2 along two guide rails 10, 11 in a left-rightdirection (also to be referred to as “scanning direction”). An endlessbelt 14 is connected to the carriage 3. Driving the endless belt 14 by acarriage drive motor 15 moves the carriage 3 in the scanning direction.

The ink-jet head 4 is installed or mounted to the carriage 3 to movetogether with the carriage 3 in the scanning direction. The ink-jet head4 includes four head units 16 arranged in the scanning direction. Thefour head units 16 are connected to a cartridge holder 7, to which inkcartridges 17 of four colors (black, yellow, cyan, and magenta) aremounted, via unillustrated tubes. Each of the head units 16 includesnozzles 24 (see FIGS. 2 to 4) formed in the lower surface thereof (theback side with respect to the paper surface of FIG. 1). The inkssupplied from the ink cartridges 17 are discharged to the recordingsheet 100 placed on the platen 2 from the nozzles 24 of the head units16.

The conveyance mechanism 5 includes two conveyance rollers 18, 19disposed to interpose the platen 2 in the front-rear direction. Theconveyance mechanism 5 conveys the recording sheet 100 placed on theplaten 2 forward (to be also referred to as “sheet conveyancedirection”) by means of the two conveyance rollers 18, 19.

The controller 6 includes a Read Only Memory (ROM), a Random AccessMemory (RAM), an Application Specific Integrated Circuit (ASIC)including various control circuits, and the like. The controller 6controls the ASIC to perform various processes, such as printing on therecording sheet 100, in accordance with programs stored in the ROM. Forexample, in a case of the printing process, the controller 6 controlsthe ink-jet head 4, the carriage drive motor 15, and the like to performthe printing of an image or the like on the recording sheet 100 on thebasis of a printing command inputted from an external device such as apersonal computer. Specifically, the controller 6 alternately performsink discharge operation and sheet conveyance operation. In the inkdischarge operation, the ink is discharged while the ink-jet head 4 andthe carriage 3 are being moved in the scanning direction. In the sheetconveyance operation, the recording sheet 100 is conveyed by theconveyance rollers 18, 19 in the sheet conveyance direction by apredetermined amount.

<Details of Ink-jet Head>

Subsequently, an explanation will be made about the detail configurationof the ink-jet head 4. Since the four head units 16 of the ink-jet head4 have the same configuration, one of the head units 16 will beexplained and any explanation of the other three head units 16 will beomitted.

As depicted in FIGS. 2 to 4, the head unit 16 includes a channelsubstrate 20, a nozzle plate 21, a piezoelectric actuator 22, and areservoir forming member 23. In FIG. 2, for the purpose of a simpleillustration, the reservoir forming member 23 disposed above the channelsubstrate 20 and the piezoelectric actuator 22 is depicted by two-dotchain lines to show its external form. Further, a COF 50 clearlydepicted in FIG. 4 is depicted by two-dot chain lines in FIGS. 2 and 3.

<Channel Substrate>

The channel substrate 20 is a single crystal silicon substrate. Thechannel substrate 20 includes pressure chambers 26. As depicted in FIGS.2 and 3, each of the pressure chambers 26 has a rectangular planar shapeelongated in the scanning direction. The pressure chambers 26 arearranged in the sheet conveyance direction to form two pressure chamberrows disposed in the scanning direction. The channel substrate 20further includes a vibration film 30 covering the pressure chambers 26.The vibration film 30 is a film made of silicon dioxide (SiO₂) orsilicon nitride (SiN_(x)) which is obtained by oxidizing or nitriding apart of the silicon channel substrate 20. The vibration film 30 includescommunicating holes 30 a through which the channels in the reservoirforming member 23 communicate with the pressure chambers 26respectively.

<Nozzle Plate>

The nozzle plate 21 is joined to the lower surface of the channelsubstrate 20. The nozzle plate 21 includes the nozzles 24 communicatingwith the pressure chambers 26 of the channel substrate 20 respectively.Similar to the pressure chambers 26, the nozzles 24 are arranged in thesheet conveyance direction to form two nozzle rows 25 a, 25 b disposedin the scanning direction, as depicted in FIG. 2. The nozzles 24 of thenozzle row 25 a are arranged to be deviated from the nozzles 24 of thenozzle row 25 b in the sheet conveyance direction by a half (P/2) of anarrangement pitch P of each nozzle row 25. The material of the nozzleplate 21 is not especially limited. Various materials including, forexample, a metal material such as stainless steel and a synthetic resinmaterial such as silicon or polyimide can be used for nozzle plate 21.

<Piezoelectric Actuator>

The piezoelectric actuator 22 applies discharge energy to the ink in thepressure chambers 26 so as to discharge the ink from the nozzles 24. Thepiezoelectric actuator 22 is disposed on the upper surface of thevibration film 30 of the channel substrate 20. As depicted in FIGS. 2 to4, the piezoelectric actuator 22 includes piezoelectric elements 39which are disposed on the upper surface of the vibration film 30 tocorrespond to the pressure chambers 26 in two rows.

In the following, the configuration of each piezoelectric element 39 ofthe piezoelectric actuator 22 and the configuration associated therewithwill be explained in that order. Each piezoelectric element 39 includesa lower electrode 31, a piezoelectric part 37, and an upper electrode33.

The lower electrode 31, which is provided for each piezoelectric element39, is disposed in an area overlapping with the piezoelectric chamber 26on the upper surface of the vibration film 30. Namely, the lowerelectrode 31 is an individual electrode which is individually providedfor each piezoelectric element 39. The lower electrode 31 is made ofplatinum (Pt). The shape of each lower electrode 31 is not especiallylimited. For example, FIG. 3 depicts the lower electrodes 31, each ofwhich has a rectangular planar shape smaller than the pressure chamber26 corresponding thereto. The lower electrode 31 includes a connectionpart 31 a at one end in its longitudinal direction as viewed from above.Each connection part 31 a is connected to a trace 35 which will bedescribed later. The connection part 31 a extends toward the sideopposite to the communicating hole 30 a with respect to the pressurechamber 26 corresponding thereto.

As depicted in FIG. 2, two piezoelectric bodies 32, which correspond totwo pressure chamber rows respectively, are provided on the uppersurface of the vibration film 30. Each piezoelectric body 32 has arectangular planer shape elongated in the sheet conveyance direction.The parts, of each piezoelectric body 32, facing the piezoelectricchambers 26 are driving parts which apply pressure to the pressurechambers 26. The driving parts are particularly referred to as“piezoelectric parts 37”. In other words, connecting the piezoelectricparts 37 of the piezoelectric elements 39 arranged in the sheetconveyance direction to each other constitutes one piezoelectric body32. Each piezoelectric body 32 is stacked on the lower electrodes 31,which correspond to a row of the pressure chambers 26, to extend acrossthe lower electrodes 31 in the sheet conveyance direction. Namely, thelower electrodes 31 are disposed on the lower side (the vibration plateside) of the piezoelectric parts 37 forming the piezoelectric body 32.Each of the connection parts 31 a provided at the one end of the lowerelectrode 31 in its longitudinal direction extends, in the scanningdirection, slightly beyond the piezoelectric body 32 (piezoelectric part37). Each of the connection parts 31 a extending slightly beyond thepiezoelectric body 32 is connected to the trace 35.

As depicted in FIG. 4, the left side surface and right side surface ofthe piezoelectric body 32 are inclined inward to a plane perpendicularto the vibration film 30. The piezoelectric body 32 has a taperedcross-sectional shape in which the upper surface is smaller than thelower surface. The piezoelectric body 32 is made of, for example, apiezoelectric material composed primarily of lead zirconate titanate(PZT) which is a mixed crystal of lead titanate and lead zirconate. Or,the piezoelectric body 32 may be made of a lead-free piezoelectricmaterial containing no lead.

The upper electrode 33 is formed on the upper surface of eachpiezoelectric body 32. The upper electrode 33 extends in the sheetconveyance direction across the lower electrodes 31 of the piezoelectricelements 39 while sandwiching the piezoelectric body 32 between theupper electrode 33 and the lower electrodes 31. Namely, the upperelectrode 33, which faces, in common, the lower electrodes 31 arrangedin the sheet conveyance direction, is a common electrode for thepiezoelectric elements 39. In other words, the electrode portions, ofthe upper electrode 33, which face the lower electrodes 31 respectively,are formed integrally to electrically connect to each other. The upperelectrode 33 can be made of iridium (Ir) or the like.

As depicted in FIGS. 3 and 4, each upper electrode 33 extending in thesheet conveyance direction includes, at both ends in the scanningdirection, two conductive parts 34 extending in the sheet conveyancedirection. Each conductive part 34 is made of gold (Au). Each conductivepart 34 has a width smaller than that of the upper electrode 33, but hasa considerably larger thickness than that of the upper electrode 33.Providing the two conductive parts 34 having the large thickness at bothends of the upper electrode 33 in the scanning direction reduces theelectrical resistance of the entire common electrode, and reducing thethickness of the upper electrode 33 extending across the upper surfacesof the piezoelectric parts 37 prevents deformation impediment whichwould be otherwise caused in each piezoelectric part 37. As understoodfrom FIG. 2, the two conductive parts 34 disposed on left and rightsides are electrically connected to each other at both ends in the sheetconveyance direction.

The portion (to be referred to as an active portion 37 a), of eachpiezoelectric part 37, sandwiched between the lower electrode 31 and theupper electrode 33 is polarized upward in the thickness direction of thepiezoelectric part 37, i.e., the active portion 37 a is polarized in thedirection oriented from the lower electrode 31 to the upper electrode33.

As depicted in FIGS. 2 to 4, the traces 35, which correspond to thepiezoelectric elements 39 respectively, are disposed on the uppersurface of the vibration film 30. Each of the traces 35 is made of gold(Au). Each of the traces 35 includes a gold layer and a thin base layer.The thin base layer, called an adhesion layer or seed layer, istypically provided on the lower side of the gold layer to improveadhesiveness or to form the trace 35 through film formation, plating, orthe like. The base layer is made, for example, of titanium tungsten. Inthe trace 35, the gold layer has a thickness, for example, in a range of50 to 90 nm, and the base layer has a thickness, for example, in a rangeof 50 to 100 nm.

Each of the traces 35 is disposed as follows. Namely, one end of thetrace 35 is disposed at an end of the piezoelectric part 37 of thecorresponding piezoelectric element 39 on the connection part 31 a side.The trace 35 extends along the upper surface of the piezoelectric part37 to the side opposite to the active portion 37 a, extends downwardalong the inclined side surface of the piezoelectric part 37, and coversthe connection part 31 a of the lower electrode 31 extending beyond thepiezoelectric part 37. Namely, the one end of each trace 35 runs on theend of the piezoelectric part 37 on the connection part 31 a side andthe connection part 31 a. Arranging a part of the trace 35 to overlapwith a part of the piezoelectric part 37 enhances the connectionreliability between the trace 35 and the lower electrode 31. Note that,a metal protective film 38, which protects each lower electrode 31, isformed to extend from the upper surface of the end of the piezoelectricpart 37 on the connection part 31 a side to the upper surface of theconnection part 31 through the side surface of the piezoelectric part37. The upper surface of the metal protective film 38 is covered withthe one end of the trace 35. The metal protective film 38 protects thelower electrode 31, specifically, prevents the lower electrode 31 frombeing cut or scraped when the upper electrode 33 is patterned byetching. The metal protective film 38 is made of the same material asthe upper electrode 33, such as iridium (Ir), through the samefilm-formation process as the upper electrode 33. Further, two traces36, which are connected to each upper electrode 33, are formed on theupper surface of the vibration film 30. Each trace 36 is made of gold(Au) in a similar manner to each trace 35 connected to the lowerelectrode 31.

The trace 35 extends in the scanning direction parallel to the planerdirection of the vibration film 30 through the position contacting withthe connection part 31 a of the lower electrode 31. More specifically,as depicted in FIG. 2, the traces 35 connected to the lower electrodes31 arranged on the left side extend leftward from the lower electrodes31 corresponding thereto, and the traces 35 connected to the lowerelectrodes 31 arranged on the right side extend rightward from the lowerelectrodes 31 corresponding thereto. Each of the traces 35 has a drivecontact portion 40 at an end on the side opposite to the tower electrode31. The drive contact portions 40 of the traces 35 are arranged, in thesheet conveyance direction, at left and right ends of the channelsubstrate 20 (vibration film 30). The two traces 36, which are connectedto each upper electrode 33, also extend from each upper electrode 33 inthe scanning direction. Each of the traces 36 has a ground contactportion 41 at an end thereof. The ground contact portions 41 aredisposed into alignment with the drive contact portions 40 at left andright ends of the channel substrate 20 (vibration film 30).

For the purpose of improving the reliability of electrical connection bypreventing, for example, disconnection of the trace 35, or for thepurpose of reducing the electrical resistance of the trace 35, it ispreferred that the thickness of the trace 35 be greater than apredetermined thickness. However, since the trace 35 is made ofexpensive gold, the increase in thickness of the trace 35 leads to thegreat increase in manufacturing costs. Thus, in this embodiment, eachtrace 35 is stacked on a metal part 43 to increase the substantialthickness of the trace 35 while preventing the increase in manufacturingcosts.

As depicted in FIGS. 2 to 4, the metal part 43 is positioned on thelower side of each trace 35 (the side of the vibration film 30). Themetal part 43 has a thickness greater than that of the trace 35 stackedthereon, as depicted in FIG. 4. For example, the thickness of the metalpart 43 is not less than 200 nm. The width of the gold trace 35 isgreater than that of the metal part 43 positioned on the lower sidethereof. The gold trace 35 completely covers the metal part 43. Themetal part 43 is formed on the vibration film 30 at a position outsidethe piezoelectric body 32 (piezoelectric part 37) in the scanningdirection. Namely, the metal part 43 does not overlap with thepiezoelectric body 37. The metal part 43 may be made of any materialexcept for gold. It is preferred that the metal part 43 is made of ametal material having low electrical resistivity such as copper (Cu) oraluminum (Al).

As depicted in FIG. 2, a metal part 44 made of a material except forgold is disposed on the lower side of each gold trace 36 connected toeach upper electrode 33 as the common electrode. This configuration, inwhich each trace 36 used for the common electrode is stacked on themetal part 44, increases the substantial thickness of the trace 36. Thewidth of the gold trace 36 is greater than that of the metal part 44positioned on the lower side thereof. The gold trace 36 completelycovers the metal part 44.

As depicted in FIGS. 2 to 4, two COFs 50 are joined to left and rightends of the vibration film 30 of the channel substrate 20. Contactportions 55 a of front ends of traces 55 formed in the COFs 50 areelectrically connected to the drive contact portions 40 respectively.Although illustration is omitted, each COF 50 is also connected to thecontroller 6 (see FIG. 1) of the printer 1.

A driver IC 51 is mounted on each COF 50. The driver IC 51 generates adriving signal for driving the piezoelectric actuator 22 on the basis ofa control signal transmitted from the controller 6 and outputs it. Thedriving signal outputted from the driver IC 51 is inputted to each drivecontact portion 40 via each trace 55 of the COF 50, and then is suppliedto each lower electrode 31 via each trace 35 of the piezoelectricactuator 22. The electric potential of the lower electrode 31 to whichthe driving signal is supplied changes between a predetermined drivingpotential and a ground potential. Each COF 50 also includes groundtraces (not depicted), and the ground traces are electrically connectedto the ground contact portions 41 of the piezoelectric actuator 22.Thus, the electric potential of the upper electrodes 33 connected to theground contact portions 41 is always kept in the ground potential.

When the contact portions 55 a of the traces 55 of the COFs 50 are madeof gold, it is preferred that the contact portions 55 a of the traces 55of the COFs 50 be diffusion-joined to the drive contact portions 40 ofthe traces 35. For example, pressing the COB 50 against the channelsubstrate 20 while heating the channel substrate 20 diffuses gold atomsbetween the drive contact portions 40 of the traces 35 and the contactportions 55 a of the COFs 50 which are made of the same material,thereby joining the drive contact portions 40 and the contact portions55 a. If the joining or bonding is performed by using an electricallyconductive joining material such as solder, the joining material flowsout to the circumference. Thus, when the traces 35 are disposed at anarrow pitch, the traces 35 disposed adjacently to each other are liableto have short circuit. The diffusion-joining, however, causes no shortcircuit between the traces 35 disposed adjacently to each other at thenarrow pitch. Namely, the diffusion-joining can join the contactportions 55 a of the traces 55 of the COFs 50 and the drive contactportions 40 of the traces 35 without suffering from the above problem.

An explanation will be made about the operation of the piezoelectricactuator 22 at the time of supplying the driving signal from the driverIC 51. The electric potential of the lower electrode 31 is the groundpotential in a state that no driving signal is supplied, and thus theelectric potential of the lower electrode 31 is the same as that of theupper electrode 33 in this state. When the driving signal is supplied tothe lower electrode 31 kept in the ground potential so that the drivingpotential is applied thereto, the potential difference between the lowerelectrode 31 and the upper electrode 33 occurs. This generates anelectric field in the active portion 37 a of the piezoelectric part 37.The electric field is parallel to the thickness direction of thepiezoelectric part 37. Since the polarization direction of the activeportion 37 a is coincident with the direction of the electric field, theactive portion 37 a extends in its thickness direction being thepolarization direction, and contracts in its planer direction. Thecontraction deformation of the active portion 37 a bends the vibrationfilm 30, so that the vibration film 30 becomes convex toward thepressure chamber 26. This reduces the volume of the pressure chamber 26to generate the pressure wave in the pressure chamber 26, therebydischarging liquid droplets of ink from the nozzle 24 communicating withthe pressure chamber 26.

<Reservoir Forming Member>

As depicted in FIG. 4, the reservoir forming member 23 is disposed onthe opposite side (upper side) of the channel substrate 20 with thepiezoelectric actuator 22 interposed therebetween. The reservoir formingmember 23 is joined to the upper surface of the piezoelectric actuator22. Similar to the channel substrate 20, the reservoir forming member 23may be made, for example, of silicon. Or, the reservoir forming member23 may be made, for example, of a material except for silicon, such as ametal material or synthetic resin material.

As depicted in FIG. 4, a reservoir 52 extending in the sheet conveyancedirection is formed at an upper half part of the reservoir formingmember 23. The reservoirs 52 are connected to the cartridge holder 7(see FIG. 1) to which the ink cartridges 17 are attached viaunillustrated tubes.

Ink supply channels 53 extending downward from the reservoir 52 areformed at a lower half part of the reservoir forming member 23. The inksupply channels 53 communicate with the communicating holes 30 a formedin the vibration film 30 of the piezoelectric actuator 22. Thisconfiguration supplies the ink from the reservoir 52 to the pressurechambers 26 of the channel substrate 20 via the ink supply channels 53and the communicating holes 30 a. A protective cover 54 is formed at thelower half part of the reservoir forming member 23 to cover thepiezoelectric elements 39 of the piezoelectric actuator 22. Theprotective cover 54 has no wall on the side opposite to the ink supplychannels 53 (right side in FIG. 4), and thus the space where thepiezoelectric elements 39 are accommodated opens sideward.

Next, an explanation will be made about a step of manufacturing theink-jet head 4 with reference to FIGS. 5A to 5C, FIGS. 6A to 6D, andFIGS. 7A to 7C. Especially, the explanation will focus on a step ofmanufacturing the piezoelectric actuator 22.

In this embodiment, the piezoelectric actuator 22 including thepiezoelectric elements 39 is manufactured by sequentially stackingvarious films on the vibration film 30 of the channel substrate 20through a film formation step such as spattering and a patterning stepsuch as etching to be repeatedly performed. As depicted in FIG. 5A, thevibration film 30 such as silicon dioxide is at first formed on thesurface of the channel substrate 20 by thermal oxidation or the like.Further, the communicating hole 30 a is formed on the vibration film 30by etching. Next, as depicted in FIG. 5B, each lower electrode 31 madeof platinum is formed on the vibration film 30. Then, as depicted inFIG. 5C, a piezoelectric material film is formed on each lower electrode31 by a sol-gel method or spattering, and the piezoelectric materialfilm is patterned by etching. Accordingly, the piezoelectric body 32(piezoelectric part 37) is formed. At the time of forming thepiezoelectric material film, thermal treatment for annealing isperformed as appropriate.

As depicted in FIG. 6A, a conductive film 60, such as iridium, whichwill be the upper electrode 33, is formed on the upper surface of thepiezoelectric body 32. Next, as depicted in FIG. 6B, the conductive film60 is etched to form the upper electrode 33 and the metal protectivefilm 38 at the same time. Next, as depicted in FIG. 6C, the metal part43, which is made of a metal material other than gold, is formed on apart, of the upper surface of the vibration film 30, where the trace 35is to be formed thereon. Next, as depicted in FIG. 6D, the trace 35 andthe conductive parts 34 are formed. Namely, the gold trace 35 is formedon the metal protective film 38 and the metal part 43 and the goldconductive parts 34 are fumed on the upper electrode 33. The gold trace35 and the gold conductive parts 34 can be formed, for example, byplating at the same time. In the plating, a resist pattern is at firstformed, and then a seed layer, which is abase layer, is formed on anarea having no resist pattern. Next, the resist pattern is peeled offand a gold layer is formed on the seed layer by plating. Namely, thetrace 35 is formed of two layers including the seed layer as the baselayer and the gold layer formed on the seed layer. The manufacture ofthe piezoelectric actuator 22 having the piezoelectric elements 39 iscompleted by performing the above steps.

In FIGS. 6A to 6C, the metal part 43 is formed after the formation ofthe lower electrode 31, the piezoelectric body 32, and the upperelectrode 33. The metal part 43, however, may be formed before theformation of the lower electrode 31, the piezoelectric body 32, and theupper electrode 33. Namely, the formation of the piezoelectric body 32(film formation, etching) may be performed after the formation of themetal part 43. Or, the formation of the lower electrode 31, theformation of the piezoelectric body 32, and the like may be performedafter the formation of the metal part 43.

As depicted in FIG. 7A, the channel substrate 20 is etched from itslower surface on the side opposite to the piezoelectric actuator 22,thereby forming the pressure chamber 26. Next, as depicted in FIG. 7B,the nozzle plate 21 is joined to the lower surface of the channelsubstrate 20 by adhesive. Lastly, as depicted in FIG. 7C, the reservoirforming member 23 is joined to the piezoelectric actuator 22 byadhesive.

In the embodiment, the trace 35 connected to the lower electrode 31 isstacked on the metal part 43, and thus the substantial thickness of thetrace 35 has become thick, as depicted in FIG. 4. This preventsdisconnection of the trace 35, thereby improving the reliability ofelectrical connection. Further, the effect of reducing substantialelectrical resistance of the trace 35 can be obtained. Especially, whenthe metal part 43 is thicker than the trace 35, the reliability ofelectrical connection of trace 35 greatly improves and the substantialelectrical resistance of trace 35 greatly lowers.

The metal part 43 is made of a metal material except for gold. Usinginexpensive metal material for the metal part 43 can reduce materialcosts, enhance the reliability of electrical connection of the trace 35,and reduce the electrical resistance of trace 35. As depicted in FIG. 2,the traces 36 connected to the upper electrodes 33 as the commonelectrodes are stacked on the metal parts 44. Thus, the traces 36 usedfor the common electrodes can have improved electrical connectionreliability and lowered electrical resistance.

As depicted in FIGS. 2 and 3, the widths of the traces 35, 36 made ofgold are respectively greater than the widths of the metal parts 43, 44.Covering the metal parts 43, 44 with the gold traces 35, 36 prevents thedeterioration of the metal parts 43, 44 made of a material except forgold.

The metal parts 43 are disposed only in areas, of the vibration film 30,which do not overlap with the pressure chambers 26. This allows thevibration film 30 and the piezoelectric parts 37 covering the pressurechambers 26 to be deformed without being impeded.

In the above embodiment, the ink-jet head 4 corresponds to a liquiddischarge apparatus of the present teaching. The lower electrode 31corresponds to a first electrode of the present teaching. The upperelectrode 33 corresponds to a second electrode of the present teaching.The traces 35, 36 each correspond to a gold trace of the presentteaching. The metal parts 43, 44 each correspond to a first metal partof the present teaching. Each of the COFs 50 corresponds to a wiringmember of the present teaching.

Subsequently, an explanation will be made about modified embodiments inwhich various changes or modifications are added to the aboveembodiment. The constitutive parts or components, which are the same asor equivalent to those of the above embodiment, are designated by thesame reference numerals, any explanation of which will be omitted asappropriate.

In the above embodiment, the traces 35 connected to the lower electrodes31 and the traces 36 connected to the upper electrodes 33 are stacked onthe metal parts 43, 44 respectively. However, one of the traces 35, 36may not be stacked on the corresponding metal parts. When the traces 35connected to the lower electrodes 31 are compared to the traces 36connected to the upper electrodes 33, the traces 36 (two traces 36 inthe above embodiment) can be connected with each upper electrode 33 asthe common electrode, whereas only one fine trace (the trace 35) isconnected with each lower electrode 31 as the individual electrode.Thus, in view of obtaining the reliability of electrical connection, itis preferred that the traces 35 connected to the lower electrodes 31 asthe individual electrodes are stacked on the metal parts 43.

In the above embodiment, the metal parts 43, 44 disposed on the lowerside of the traces 35, 36 are thicker than the traces 35, 36 disposed onthe upper side of the metal parts 43, 44. The thicknesses of the metalparts 43, 44, however, may be the same as or thinner than thethicknesses of the traces 35, 36.

In the above embodiment, the piezoelectric parts 37 of the piezoelectricelements 39 arranged in a nozzle arrangement direction (sheet conveyancedirection) are connected to each other to form one piezoelectric body32, as depicted in FIGS. 2 and 3. The piezoelectric parts 37 of thepiezoelectric elements 39, however, may be separated from each other.

In the above embodiment, the piezoelectric actuator 22 includes thelower electrodes 31, each of which is the individual electrodeindividually provided for each of the piezoelectric elements 39, and theupper electrodes 33, each of which is the common electrode commonlyprovided for the piezoelectric elements 39. The present teaching,however, can be applied to piezoelectric elements of which electrodesare reversely arranged relative to the arrangement of the aboveembodiment, i.e., piezoelectric elements each including a lowerelectrode as the common electrode and an upper electrode as theindividual electrode.

In a piezoelectric element 69 depicted in FIG. 8, a trace 65 made ofgold is connected to an upper electrode 63 as the individual electrodewhich is disposed on the upper surface of the piezoelectric part 37. Thetrace 65 extends from the upper surface of an end (right end in FIG. 8)of the upper electrode 63, extends downward along the side surface ofthe piezoelectric part 37, and extends along the vibration film 30 witha metal part 73 interposed between the trace 65 and the vibration film30. The metal part 73 is disposed on the lower side (the vibration film30 side) of the trace 65.

When the lower electrode 61 is made of expensive platinum, it ispreferred that the lower electrode 61 is thin to reduce costs. However,when the lower electrode 61, which is the common electrode, has a smallthickness, the electrical resistance of the common electrode increases.This causes a harmful effect on the behaviors (responsiveness and thelike) of each piezoelectric element 69.

Thus, as depicted in FIG. 9, the lower electrode 61 made of platinum maybe stacked on a metal part 75 made of a material other than platinum. Itis preferred that the metal part 75 is made of the same material (amaterial other than gold and platinum) as the metal part 73, which isdisposed on the lower side of the gold trace 65 connected to the upperelectrode 63, through the same film formation process. In thisconfiguration, the trace 65 connected to the upper electrode 63 isstacked on the metal part 73 and the lower electrode 61 is stacked onthe metal part 75. Thus, two metal parts 73, 75 are separated from eachother, namely, they are not electrically connected to each other. Themetal part 75 in the embodiment depicted in FIG. 9 corresponds to asecond metal part of the present teaching.

As described above, the lower electrode 61 as the common electrode isstacked on the metal part 75 made of a material other than gold andplatinum. Thus, the thickness of the lower electrode 61 made of platinumcan be reduced to prevent material cost increase, and the substantialelectrical resistance of the lower electrode 61 can be reduced. Forexample, the thickness of the lower electrode 61 made of platinum can bereduced to 0.1 μm or less (preferably, 0.05 μm or less). The metal part75 is made of the same material as the metal part 73 disposed on thelower side of the trace 65 through the same film formation process, andthus no process is added to form the metal part 75.

The material of the metal part 75 is not especially limited providedthat the material is other than gold and platinum. However, when themanufacturing steps of the piezoelectric actuator include a heatingprocess under high temperature (for example, annealing of thepiezoelectric part 37), it is preferred that the metal part 75 is madeof a metal material with a high melting point such as zirconium,tantalum, or tungsten.

In FIG. 9, the metal part 75 is disposed on the lower side (thevibration film 30 side) of the lower electrode 61 made of platinum. Themetal part 75, however, may be disposed on the upper side of the lowerelectrode 61. Note that, various heating processes, such as theannealing of the piezoelectric material film as described above, areperformed in the manufacture of the piezoelectric actuator 22. One ofthe reasons the lower electrode 61 is made of platinum is because metalatoms constituting the lower electrode 61 are less likely to diffuse tothe piezoelectric part 37 during various heating processes, such as theannealing of the piezoelectric part 37. That is, when the metal part 75made of a material other than platinum is stacked on the lower electrode61 made of platinum, metal constituting the metal part 75 is more likelyto diffuse to the piezoelectric part 37 during heating processes. Thus,it is preferred that the metal part 75 is disposed on the lower side ofthe lower electrode 61 made of platinum, as depicted in FIG. 9.

In FIG. 9, the metal part 75 disposed on the lower side of the lowerelectrode 61 has the same thickness as the metal part 73 disposed on thelower side of the trace 65. The two metal parts 73, 75, however, mayhave mutually different thicknesses. Especially, since the metal part 75is disposed on the lower side of the lower electrode 61 so that thepiezoelectric part 37 overlaps with the metal part 75, the metal part 75having a very large thickness impedes the deformation of thepiezoelectric part 37. Thus, the metal part 75 disposed on the lowerside of the lower electrode 61 may be thinner than the metal part 73disposed on the lower side of the trace 65. Such a configuration can beobtained, for example, as follows. Namely, two metal parts 73, 75 areformed through the same film formation process, and then etching isperformed for the metal part 75 to reduce the thickness thereof.

When the lower electrode 61 is stacked on the metal part 75, the metalpart 75 impedes the deformation of the piezoelectric part 37. Thus, asdepicted in FIG. 10A, the thickness of the metal part 75 in a first areaA of the lower electrode 61 may be a smaller than a thickness of themetal part 75 in other areas. The first area A includes an area whichfaces at least the upper electrode 63 with the piezoelectric part 37interposed therebetween (an area on which the active portion 37 a isdisposed). In this configuration, the metal part 75 is less likely toimpede the deformation of the piezoelectric part 37. Further, the metalpart 73 disposed on the lower side of the trace 35 and the metal part 75disposed on the lower side of the lower electrode 61 are formed throughthe same film formation process in this configuration.

In FIG. 10A, a part (left end in FIG. 10A) of a thin portion 75 a of themetal part 75 is exposed from the piezoelectric part 37. In this case,when a process, such as patterning of the upper electrode 63 through dryetching, is performed after formation of the piezoelectric part 37, thelower electrode 61 made of platinum is cut or scraped. This may cause apart of the piezoelectric element 69 to have a small thickness. To solvesuch a problem in which the film thickness becomes partially thin in thesubsequent step, the part, of the metal part 75, exposed from thepiezoelectric part 37 may have a thickness larger than an unexposed partof the metal part 75. Alternatively, as depicted in FIG. 10B, thepiezoelectric part 37 may cover the entire thin portion 75 a of themetal part 75 stacked on the lower electrode 61.

FIG. 11 is a cross-sectional view taken along the line XI-XI in FIG.10A. As depicted in FIG. 11, the potential difference generated betweenthe upper electrode 63 and the lower electrode 61 contracts thepiezoelectric part 37, thereby bending the vibration film 30 as depictedby two-dot chain lines in FIG. 11. In this situation, steps 75 b of themetal part 75 (i.e., outer periphery of an area, of the lower electrode61, stacked on the thin portion 75 a) are preferably disposed on theouter sides of positions (positions X depicted by dot-and-dash lines)where the deformation curvature of the vibration film 30 obtained whenthe vibration film 30 is bent by the deformation of the piezoelectricpart 37 is maximum. Namely, the metal part 75 has a small thickness atthe positions where the vibration film 30 has greatest deformation orcurve, and thus the metal part 75 is less likely to impede the bendingof the vibration film 30 due to the deformation of the piezoelectricpart 37.

The metal part 75 may be formed of a plurality of layers. In FIG. 10C,the metal part 75 disposed on the lower side of the lower electrode 61includes two layers, i.e., a first layer 81 disposed on the lower sideand a second layer 82 disposed on the upper side. The metal part 75formed of the plurality of layers has the following advantages.

When the metal part 75 formed of one layer is etched to have thinportions 75 a, an etching error may cause the thin portions 75 apositioned below the active portions 37 a to have different thicknessesamong piezoelectric elements 69. When thicknesses of the thin portions75 a vary among the piezoelectric elements 69, deformationcharacteristics vary among the piezoelectric parts 37 and dischargecharacteristics vary among the nozzles 24. In the configuration depictedin FIG. 10C, however, the metal part 75 has two layers including thelower first layer 81 and the upper second layer 82. At first, the firstlayer 81 is formed on almost the entire upper surface of the vibrationfilm 30. Next, the second layer 82 is formed on the first layer 81.Then, only the second layer 82 is etched to remove the second layer 82disposed in the first area A, thereby forming the thin portion 75 a ofthe metal part 75. Namely, no etching is performed for the first layer81, and thus the thickness of the thin portion 75 a means the thicknessof the first layer 81. The variation in thicknesses of thin portions 75a of the piezoelectric elements 69 is prevented, accordingly. Further,as depicted in FIG. 10C, an edge 82 a, which is formed by partiallyremoving the second layer 82 through etching, is preferably formed intoan inclined surface so that the lower electrode 61 is easily formed onthe edge 82 a through sputtering or the like in a subsequent step. Or,the edge 82 a of the second layer 82 may be in a shape of stairs.

As depicted in FIG. 10D, the second layer 82 to be etched may be thelower layer, and the first layer 81 may be the upper layer. Further, asdepicted in FIG. 10E, the first layer 81 may be disposed on the lowerside of the lower electrode 61 and the second layer 82 may be disposedon the upper side of the lower electrode 61 so that they sandwich thelower electrode 61 made of platinum in an up-down direction.

The material(s) of the first layer 81 and the second layer 82 is(are)not especially limited, provided that the first layer 81 and the secondlayer 82 are made of a metal material except for gold and platinum.However, as depicted in FIG. 10C, when etching is performed for thesecond layer 82 formed on the first layer 81 after formation of thefirst layer 81, it is preferred that the first layer 81 and the secondlayer 82 are made of mutually different materials. This is because, thelower first layer 81 made of a material different from that of thesecond layer 82 is less likely to be etched when wet etching isperformed for the upper second layer 82. Meanwhile, as depicted in FIG.10D, when etching is performed for the second layer 82 before formationof the first layer 81, the first layer 81 and the second layer 82 can bemade of the same material without any problems.

When etching is performed for the second layer 82, over-etching orunder-etching may occur. The over-etching removes not only the secondlayer 82 but also the layer disposed on the lower side of the secondlayer 82. The under-etching fails to etch the second layer 82sufficiently. Here, the following manner is also allowable from anotherpoint of view. For example, when the lower first layer 81 is required toreliably have a certain thickness in the configuration depicted in FIG.10C, the under-etching may be purposefully performed for the secondlayer 82 so as not to remove the first layer 81 through etching of thesecond layer 82. Further, as depicted in FIG. 10E, when the second layer82 to be etched is disposed on the lower electrode 61 made of platinum,the over-etching may be purposefully performed for the second layer 82to reliably expose the lower electrode 61.

As depicted in FIG. 12, slits 70 may be formed at parts, of thepiezoelectric part 37, positioned on outer sides of the active portion37 a, i.e. parts, of the piezoelectric part 37, disposed in second areasB different from the first area A. This configuration facilitates thedeformation of the active portion 37 a of the piezoelectric part 37. Inthe second areas B, thick portions 75 c of the second metal part 75 aredisposed on the lower side of the lower electrode 61. The thick portions75 c of the second metal part 75 disposed on the lower side of the lowerelectrode 61 allow the lower electrode 61 to have a substantialthickness, even if the lower electrode 61 disposed on the lower side ofthe piezoelectric part 37 is cut or scraped at the time of forming theslits 70 in the piezoelectric part 37 through etching (especially,dry-etching).

FIG. 10A depicts an example in which the metal part 75 in the first areaA has a smaller thickness. Instead of this configuration, the metal part75 may not be formed in the first area A as depicted in FIG. 13A. Sincethe metal part 75 provided in this configuration does not impede thedeformation of the piezoelectric part 37, the embodiment depicted inFIG. 13A can obtain the effect of preventing the deformation impedimentin the piezoelectric part 37, similar to the embodiment depicted in FIG.10A. Further, as depicted in FIG. 13B, a part of the lower electrode 61where no metal part 75 is provided may be entirely covered with thepiezoelectric part 37, similar to the embodiment depicted in FIG. 10B.Note that a boundary between a part of the lower electrode 61 having themetal part 75 on its lower side and apart of the lower electrode 61having no metal part 75 on its lower side is preferably positioned onthe outer side of the position where the deformation curvature of thevibration film 30 obtained when the vibration film 30 is bent by thedeformation of the piezoelectric part 37 is maximum.

As depicted in FIG. 14, the metal part 75 disposed on the lower side ofthe lower electrode 61 as the common electrode may be electricallyconnected to the metal part 74 disposed on the lower side of the goldtrace 66 connected to the lower electrode 61. Although the illustrationof the trace connected to the upper electrode 63 is omitted in FIG. 14,the trace connected to the upper electrode 63 is disposed on the uppersurface of the vibration film 30 to be deviated, in a directionperpendicular to the paper surface of FIG. 14, from the trace 66connected to the lower electrode 61 depicted in FIG. 14.

The configuration of ink channel of the ink-jet head 4 is not limited tothat of the above embodiment. For example, the configuration of the inkchannel can be modified as follows. In the above embodiment, the inkchannel is configured so that the ink is supplied from the reservoir 52in the reservoir forming member 23 to the pressure chambers 26 via thecommunicating holes 30 a, as depicted in FIG. 4. Instead of the aboveconfiguration, a channel corresponding to the reservoir 52 may be formedin the channel substrate 20. For example, the following configuration isalso allowable. That is, a manifold channel extending in the arrangementdirection of the pressure chambers 26 is formed in the channel substrate20, and the ink is supplied to each of the pressure chambers 26 from themanifold channel.

In the above embodiment, as depicted in FIG. 2, the lower electrodes 31as the individual electrodes form two rows, and the traces 35 arerespectively drawn from the lower electrodes 31 to the outside in thescanning direction. Instead of the above configuration, the traces 35may be respectively drawn from the lower electrodes 31 to the inside inthe scanning direction, and the drive contact portions 40 may bedisposed between two rows of the lower electrodes 31. Or, the traces 35may be drawn from all of the lower electrodes 31 forming two rows to oneside in the scanning direction.

In the embodiment and the modified embodiments as described above, thepresent teaching is applied to a piezoelectric actuator of an ink-jethead which discharges ink on a recording sheet to print an image etc.The present teaching, however, can be also applied to a liquid dischargeapparatus used in various uses other than the printing of the image etc.For example, the present teaching can be also applied to a liquiddischarge apparatus which discharges a conductive liquid on a board toform a conductive pattern on the surface of the board.

What is claimed is:
 1. A liquid discharge apparatus, comprising: apressure chamber; a film covering the pressure chamber; a piezoelectricelement disposed on the film and including a piezoelectric part, a firstelectrode, and a second electrode, wherein the first electrode isdisposed on a first side of the piezoelectric part facing the pressurechamber, and the second electrode is disposed on a second side of thepiezoelectric part opposite the first side; a gold trace connected tothe first electrode or the second electrode; and a first metal part madeof a metal material except for gold and positioned between the film andthe gold trace, the first metal part being disposed only in an area ofthe film, which does not overlap with the pressure chamber, wherein thefirst metal part is laminated with the gold trace.
 2. The liquiddischarge apparatus according to claim 1, wherein the first metal partis thicker than the gold trace.
 3. The liquid discharge apparatusaccording to claim 1, wherein the gold trace is wider than the firstmetal part.
 4. The liquid discharge apparatus according to claim 1,wherein the first metal part is made of copper or aluminum.
 5. A liquiddischarge apparatus, comprising: a pressure chamber; a film covering thepressure chamber; a piezoelectric element disposed on the film andincluding a piezoelectric part, a first electrode, and a secondelectrode, wherein the first electrode is disposed on a first side ofthe piezoelectric part facing the pressure chamber, and the secondelectrode is disposed on a second side of the piezoelectric partopposite the first side; a gold trace connected to the first electrodeor the second electrode; and a first metal part made of a metal materialexcept for gold and positioned between the film and the gold trace,wherein the first metal part is laminated with the gold trace, wherein apart of the first electrode extends beyond the piezoelectric part to anarea outside of the pressure chamber, and wherein the gold trace isdisposed to cover the part of the first electrode extending beyond thepiezoelectric part and the gold trace partially overlaps with thepiezoelectric part.
 6. A liquid discharge apparatus, comprising: apressure chamber; a film covering the pressure chamber; a piezoelectricelement disposed on the film and including a piezoelectric part, a firstelectrode, and a second electrode, wherein the first electrode isdisposed on a first side of the piezoelectric part facing the pressurechamber, and the second electrode is disposed on a second side of thepiezoelectric part opposite the first side; a gold trace connected tothe first electrode or the second electrode; and a first metal part madeof a metal material except for gold and positioned between the film andthe gold trace, wherein the first metal part is laminated with the goldtrace, wherein the gold trace includes a gold layer and a base layerdisposed on a lower side of the gold layer and having a thicknesssmaller than a thickness of the gold layer, wherein the thickness of thebase layer is in a range of 50 to 100 nm, and wherein the first metalpart has a thickness of not less than 200 nm.
 7. A liquid dischargeapparatus, comprising: a pressure chamber; a film covering the pressurechamber; a piezoelectric element disposed on the film and including apiezoelectric part, a first electrode, and a second electrode, whereinthe first electrode is disposed on a first side of the piezoelectricpart facing the pressure chamber, and the second electrode is disposedon a second side of the piezoelectric part opposite the first side; agold trace connected to the first electrode or the second electrode; afirst metal part made of a metal material except for gold and positionedbetween the film and the gold trace; a plurality of other piezoelectricelements; and a second metal part which is disposed on the film andlaminated with the first electrode, wherein the first metal part islaminated with the gold trace, wherein the first electrode is a commonelectrode which is provided commonly for the piezoelectric element andthe plurality of other piezoelectric elements, wherein the secondelectrode is an individual electrode which is provided individually forthe piezoelectric element, wherein the first electrode is made ofplatinum, wherein the second electrode is connected to the gold trace,wherein the second metal part is made of the same metal material as thefirst metal part, wherein the metal material is different from gold andplatinum, and wherein the first metal part is separated from the secondmetal part.
 8. The liquid discharge apparatus according to claim 7,wherein the second metal part is positioned between the film and thefirst electrode.
 9. The liquid discharge apparatus according to claim 7,wherein the first electrode has a first area which includes an areafacing the second electrode with the piezoelectric part interposedtherebetween, and wherein, in the first area, no second metal part isprovided or a thickness of the second metal part is thinner than athickness of the second metal part in an area other than the first area.10. The liquid discharge apparatus according to claim 9, wherein thepiezoelectric part entirely covers the first area of the firstelectrode.
 11. The liquid discharge apparatus according to claim 9,wherein an outer periphery of the first area in the first electrode isdisposed outside of positions where a deformation curvature of the filmis at a maximum.
 12. The liquid discharge apparatus according to claim9, wherein in a second area different from the first area, thepiezoelectric part is disposed to overlap with the first electrode andthe second metal part, and a slit is formed in a part, of thepiezoelectric part, disposed on the second area.
 13. The liquiddischarge apparatus according to claim 7, wherein the second metal partis thinner than the first metal part.
 14. The liquid discharge apparatusaccording to claim 7, wherein the first metal part and the second metalpart are made of zirconium, tantalum, or tungsten.
 15. A liquiddischarge apparatus, comprising: a pressure chamber; a film covering thepressure chamber; a piezoelectric element disposed on the film andincluding a piezoelectric part, a first electrode, and a secondelectrode, wherein the first electrode is disposed on a first side ofthe piezoelectric part facing the pressure chamber, and the secondelectrode is disposed on a second side of the piezoelectric partopposite the first side; a gold trace connected to the first electrodeor the second electrode; a first metal part made of a metal materialexcept for gold and positioned between the film and the gold trace; anda plurality of other piezoelectric elements, wherein the first metalpart is laminated with the gold trace, wherein the first electrode is acommon electrode which is provided commonly for the piezoelectricelement and the plurality of other piezoelectric elements, wherein thesecond electrode is an individual electrode which is providedindividually for the piezoelectric element, wherein the first electrodeis made of platinum, wherein the second electrode is connected to thegold trace, and wherein the first electrode has a thickness of 0.1 μm orless.
 16. A liquid discharge apparatus, comprising: a pressure chamber;a film covering the pressure chamber; a piezoelectric element disposedon the film and including a piezoelectric part, a first electrode, and asecond electrode, wherein the first electrode is disposed on a firstside of the piezoelectric part facing the pressure chamber, and thesecond electrode is disposed on a second side of the piezoelectric partopposite the first side; a gold trace directly connected to the firstelectrode or the second electrode; and a first metal part made of ametal material except for gold and positioned between the film and thegold trace, wherein the first metal part is laminated with the goldtrace.